Videos of this format can be extracted with the ndstool application, a frontend for which is available at http://l33t.spod.org/ratx/DS/dslazy/ , the video files seem to use the extension .vx and starts with a signature of VXDS in the first 4 bytes.

4x4 block intra prediction seem to predict first luma mode from neighbours, the following ones use 3-bit field (plus a bit read to skip the actual prediction in each case) and has 9 methods now (top, left, DC, various angles), chroma is the same as in the previous case.

Residue is coded as groups of 8x8 semi-macroblocks made of 4x4 blocks. First there's CBP remapped from the gamma' code, top bit is for chroma blocks. Then there are coefficients for 4x4 blocks.

Coefficients are coded in 4x4 block. First there's a context-dependent static Huffman codebook for coding mode that tells how many non-zero coefficients are there and how many of them form a tail of plus-minus ones. Then there's a context dependent code for telling how many zeroes are at the end of the block. For the tail of ones only signs are coded, the rest of coefficients are coded as (gamma() << level) | get_bits(level) and then a sign where level is initially zero and is increased by one when the absolute coefficient value is greater than the limit for this level. Between coefficients there's a zero-run coded with context dependent code.